This invention relates to machine tools and grinding processes; and, more particularly, to machine tools, wheel heads, tool drive spindles, workpiece mounting and grinding processes for grinding cam lobes on cam shafts.
Many machine tools such as, for example, grinding machines, of the type shown in FIG. 1, mount a workpiece 3 for rotation between a headstock 5 and a footstock 7 which are, in turn, both mounted, in conventional manner, on a workpiece carriage 9 that is itself carried by the machine tool frame or bed 15 for reciprocating movement in the directions of arrows A and B along a workpiece axis of rotation xe2x80x9cXxe2x80x9d. The machine tool cutting tool, which may be a grinding wheel 31, is rotatively carried by a tool carriage 33 that reciprocates in the directions of arrows R and S on the machine tool frame or bed 15 in directions perpendicular to the workpiece axis of rotation xe2x80x9cXxe2x80x9d. Thus grinding wheel 31 is moved towards and into the workpiece 3 to grind the workpiece 3, or selected parts of the workpiece; and away from the workpiece 3 to permit relocation or indexing of the workpiece 3 to grind another part or portion thereof.
Generally speaking the diameter of the grinding wheel 31 is selected to be large enough so that carriage 33 and the grinding wheel 31 may be moved in the direction of arrow R a sufficient distance to grind the smallest required radial dimension for cam lobe 35; while leaving an appropriate distance between an outer surface 41 of housing, or spindle casing, 43 of tool spindle 45 and the outer surfaces of cam lobes 35. The sizing and disposition of the drive motor 47 for tool spindle 45 are also selected so that there is an appropriate spacing between motor 47 and footstock 7 when motor 47 moves with carriage 33 and tool spindle 45 in the direction of arrow R to its closest possible position to footstock 7 and cam lobes 35.
Problems, however, have been encountered with available machine tools and grinding machines when relatively small grinding wheels must be utilized to grind discrete parts, such as cam lobes 35 on cam shafts 37; and especially where re-entrant or concave cam surfaces (such as surface 61xe2x80x94FIG. 2xe2x80x94of cam lobe 63 of cam 65) are to be ground. Available constructions for spindle 45 (FIG. 1), for rotating the tool such as grinding wheel 31, and for the housing 43 enclosing such spindles 41, place a practical limit on how close the spindles"" axis of rotation xe2x80x9cyxe2x80x9d can be moved in the direction of arrow R, towards the workpiece axis of rotation xe2x80x9cxxe2x80x9d and how close the outer surfaces of the housings or casings for such tool spindles and their drive motors can be moved towards the rotating cam lobes 35.
U.S. Pat. No. 5,697,831 patented on Dec. 16, 1997, to F. Retchel for xe2x80x9cMachine Tool With Plural Tool Spindlesxe2x80x9d provides a grinding machine with dual spindles each mounting a different size grinding wheel. The drive for each such spindle is shown and described as a belt drive to the spindle from a motor that is spaced from the spindle. However, belt drives have been found undesirable for spindle speeds demanded for today""s grinding processes. To mount a conventional motor in-line with the spindle and relatively close to the grinding wheel, could create a mechanism where the motor, moving with the spindle, would interfere with and limit the travel of smaller grinding wheel towards the workpiece and thus the ability to properly grind concave surfaces. To provide an in-line motor for the spindle that is spaced from the grinding wheel would provide unacceptably long spindle shafts affecting grinding accuracy.
It is therefore an object of this invention to provide a new and novel machine tool.
It is another object of this invention to provide a new and novel grinding machine.
It is yet another object of this invention to provide a new and novel machine tool for grinding parts with at least some portion thereof concave in relationship to other portions of the surface of such parts.
It is still another object of this invention to provide a new and novel grinding machine for grinding cam lobes.
It is yet still another object of this invention to provide a new and novel grinding machine for grinding cam lobes with re-entrant curves.
It is a further object of this invention to provide a new and novel grinding process.
It is yet a further object of this invention to provide a new and novel grinding process for parts with concave surface configurations.
It is yet still a further object of this invention to provide a new and novel process for grinding cam lobes which include re-entrant or concave cam surface portions.
It is still a further object of this invention to provide a new and novel tool spindle.
It is still a further object of this invention to provide a new and novel tool spindle for a grinding machine.
It is yet still a further object of this invention to provide a new and novel grinding machine with a pair of tool spindles.
It is yet still a further object of this invention to provide a new and novel grinding machine with a first tool spindle for one or more relatively large diameter grinding wheels and a second tool spindle for relatively small diameter grinding wheels.
It is yet still a further object of this invention to provide a new and novel cam lobe grinding apparatus and process for grinding cam lobes with re-entrant or concave cam surface portions as well as convex cam surface portions.
Other objects, features and advantages of the invention in its details of construction and arrangement of parts will be seen from the above and from the following description of the preferred embodiments when considered with the drawing and from the appended claims.